US reportedly killed as many as 100 Russian fighters in Syria attack.

American military forces killed as many as 100 Russian mercenaries during an attack on a US-held base in Syria last week, according to a report on Tuesday. Scores of soldiers, mostly a mix of Russians and Ukrainians fighting on the side of Syrian strongman Bashar al-Assad, stormed the base held by US and Kurdish forces...

Time: 13:19&nbsp&nbsp&nbsp&nbsp Date: 13.02.2018

Scores of soldiers, mostly a mix of Russians and Ukrainians fighting on the side of Syrian strongman Bashar al-Assad, stormed the base held by US and Kurdish forces in the Deir Ezzor region, Bloomberg News reported.

No US casualties were reported.

The clash is believed to be the deadliest incident between US and Russian citizens since the end of the Cold War.

The attack on the base in an oil refinery may have been a rogue operation by the Russian forces, highlighting the complex civil war in Syria that has involved a grab-bag of fighters from the US, Russia, stateless Kurds, the Islamic State and local powers Iran, Turkey and Israel in the war-torn country, the report said.

Russia’s military denied any involvement and Defense Secretary James Mattis described it as “perplexing” without elaborating.

Russian forces have been propping up Assad during the seven-year war and began backing his regime with troops and firepower in 2015.

The attack began last Wednesday when pro-Assad fighters ​approached in a “battalion-sized formation supported by artillery, tanks, multiple-launch rocket systems and mortars,” Col​.​ Thomas F. Veale, a spokesman for the U.S. military, ​said in a statement to Bloomberg.

The US, which has advisers deployed alongside Syrian Democratic Forces, repelled the attack with a combination of aircraft and artillery fire.

“Coalition officials were in regular communication with Russian counterparts before, during and after the thwarted, unprovoked attack,” Veale said.

It’s unclear who was paying the contingent of Russians and Ukrainians, but reports in Russian media said a shadowy organization called Wagner, a private military contractor similar to Blackwater in the US, was hired by Assad.